Cloning and analysis of a novel conserved membrane zinc-metalloprotease family from <Emphasis Type="Italic">Solanum surattense</Emphasis>

Peptidases occur naturally in all organisms and their genes comprise 1–5% of the total number of genes. Genetic, biochemical, and molecular approaches used in recent years led to the identification and characterization of several plant organelle proteases, all of them being homologous to bacterial proteases best characterized in Escherichia coli. Here we report isolating and characterizing three novel genes, namely Sszn-mp1, Sszn-mp2, and SsZn-mp3 from Solanum surattense. To identify the subcellular location, structures, and functions of these three genes, integrated genomic approaches of data mining, expression profiling, and bioinformatic predictions were used. Sszn-mp is found to be constitutively expressed in tissues and regulated by various stimuli. Analysis of eight zinc-metalloproteases (Zn-MPs) deduced or assembled from Arabidopsis thaliana, tomato, potato, cotton, barley, sugarcane, and rice and four Zn-MPs from cyanobacteria (blue-green algae) in the GenBank database reveals that these proteins belong to a novel conserved membrane zinc-metalloprotease family. The plant Zn-MP members share more than 62% overall identity with SsZn-MP3, whereas four putative ATP-dependent zinc-proteases of cyanobacteria have low identity with SsZn-MP3 and their N-termini are about 110 amino acids shorter than those of plant Zn-MPs. The Zn-MP homologous sequences are found neither in other eukaryotic nor prokaryotic databases, suggesting that this family is specific to plants and cyanobacteria. The plant Zn-MP genes encoding membrane proteins are potentially targeted to chloroplast and plasma membranes, and the bacterial Zn-MPs are targeted to the cytoplasmic membrane, and their N-terminal targeting peptides are cleaved off for targeting the mature proteins to their subcellular compartments. The Zn-MP proteins contain a conserved zinc-binding site (HEAGHX19E/DX46∼48EX7E), a potential G-protein coupled receptors family 1 signature, and a triplet motif (N-R/K-F) in plant Zn-MPs, a D/E-R-Y motif in the four bacterial Zn-MPs, suggesting that the different mature forms of Zn-MPs may function as proteases and/or signal receptors. Published in Russian in Fiziologiya Rastenii, 2007, Vol. 54, No. 1, pp. 73–84. The text was submitted by the authors in English.     

Genomic and proteomic analyses of the coral pathogen Vibrio coralliilyticus reveal a diverse virulence repertoire

Vibrio coralliilyticus has been implicated as an important pathogen of coral species worldwide. In this study, the nearly complete genome of Vibrio coralliilyticus strain P1 (LMG23696) was sequenced and proteases implicated in virulence of the strain were specifically investigated. The genome sequence of P1 (5 513 256 bp in size) consisted of 5222 coding sequences and 58 RNA genes (53 tRNAs and at least 5 rRNAs). Seventeen metalloprotease and effector (vgrG, hlyA and hcp) genes were identified in the genome and expressed proteases were also detected in the secretome of P1. As the VcpA zinc-metalloprotease has been considered an important virulence factor of V. coralliilyticus, a vcpA deletion mutant was constructed to evaluate the effect of this gene in animal pathogenesis. Both wild-type and mutant (ΔvcpA) strains exhibited similar virulence characteristics that resulted in high mortality in Artemia and Drosophila pathogenicity bioassays and strong photosystem II inactivation of the coral dinoflagellate endosymbiont (Symbiodinium). In contrast, the ΔvcpA mutant demonstrated higher hemolytic activity and secreted 18 proteins not secreted by the wild type. These proteins included four types of metalloproteases, a chitinase, a hemolysin-related protein RbmC, the Hcp protein and 12 hypothetical proteins. Overall, the results of this study indicate that V. coralliilyticus strain P1 has a diverse virulence repertoire that possibly enables this bacterium to be an efficient animal pathogen.